Kappen Ludger, Maier Maria
Botanisches Institut II der Universität Würzburg, Würzburg, Deutschland.
Oecologia. 1973 Sep;12(3):241-250. doi: 10.1007/BF00347565.
Plants of Halimione portulacoides (L.) Aellen were grown in natural temperature and light conditions but with different concentrations of NaCl in the nutrient solution. From August 1971 to April 1972 freezing tolerance, water content, succulence, accumulation of different sugars, citrate, malate, and chloride were simultaneously determined. If no NaCl was supplied the chloride content of the leaves decreased continuously within the period of investigation. During repeated and increasing addition of NaCl the chloride content of the leaves generally increased. However, there was a reversible decrease during the frost period, although no new leaves were formed and loss through leaves and dilution of the nutrient medium by precipitation was prevented (Fig. 1).In spite of being in minimum the chloride content was relatively high in winter. No regulation of the concentration by increase of succulence was observed. The concentration did, however, increase due to a diminished water uptake in the coldest period.Sugars, which are regarded as protective agents against the influence of freezing and salts, accumulated only slightly in the frost period. Predominantly sucrose, raffinose and stachyose were remarkable. Their concentration was not sufficient to compensate the salt burden and thus could not increase the freezing tolerance. The sugar content was even lowered when the salt content was higher. In contrast, citrate and to a lesser extent malate were intensively increased in the cold season (Fig. 3). Thus organic acid to chloride ratios of between 1:2 and 1:6 were established for Halimione, which expresses the effective protection of the membrane systems against freezing injury (Fig. 4), as has been shown in vitro for e.g. spinach chloroplasts by Santarius (1971). Accumulation of these acids was even enhanced by an increasing salt burden. Consequently accumulation of organic acids or their salts such as citrate and probably malate indicates an adaptation of halophytes, which enables them to survive freezing under salt stress on the sea shore and in cold desert regions during the winter.
将盐地碱蓬（Halimione portulacoides (L.) Aellen）植株置于自然温度和光照条件下，但营养液中NaCl浓度不同。在1971年8月至1972年4月期间，同时测定了其抗冻性、含水量、肉质化程度、不同糖类、柠檬酸盐、苹果酸盐和氯化物的积累情况。如果不供应NaCl，在研究期间叶片中的氯化物含量会持续下降。在反复增加NaCl供应时，叶片中的氯化物含量总体上会增加。然而，在霜冻期会出现可逆性下降，尽管没有新叶形成，且防止了因叶片脱落和降水对营养液的稀释导致的损失（图1）。尽管冬季氯化物含量处于最低水平，但相对较高。未观察到通过增加肉质化程度来调节浓度的情况。然而，在最冷时期由于水分吸收减少，浓度确实增加了。被视为抵御冷冻和盐分影响的保护剂的糖类，在霜冻期仅略有积累。主要是蔗糖、棉子糖和水苏糖较为显著。它们的浓度不足以补偿盐分负担，因此无法提高抗冻性。当盐分含量较高时，糖含量甚至会降低。相比之下，柠檬酸盐以及程度稍轻的苹果酸盐在寒冷季节会大量增加（图3）。因此，盐地碱蓬的有机酸与氯化物的比例在1:2至1:6之间，这表明膜系统得到了有效保护，免受冻害（图4），正如Santarius（1971年）在体外对例如菠菜叶绿体所显示的那样。盐分负担增加甚至会增强这些酸的积累。因此，有机酸或其盐类如柠檬酸盐以及可能的苹果酸盐的积累表明盐生植物的一种适应性，使其能够在冬季盐胁迫下在海岸和寒冷沙漠地区的冷冻条件下存活。
